The ability of life to adapt, from its evolution under primordial conditions to its future survival under increasing temperatures, is a subject of fascination. As far as we know, microbes which are similar to those found today have been on Earth for billions of years. Across this great time span, how could life adapt in the face of continuously changing conditions? An analysis of the genomes of some of the most ancient organisms, called methanogens, reveals that, despite growing across a wide range of temperatures, methanogens have surprisingly similar genomes. However, they exhibit variations in amino acid compositions, indicating that temperature adaptation could result from fine scale adaptations, rather than large changes in genomic composition and the use of many temperature specific proteins.